How do I model something like a rail station?
I don't need to make something super accurate or usable in actually building the railway?
I have some idea about how to position the rails and platforms at a terminus of a metro line such that it would allow for easy transfer between the metro lines, and I want to make a crude 3D model to demonstrate this.
Do I need to learn AutoCAD Civil 3D to do this?
maybe, yes
if its just a simulation you can assist array and curve modifiers
>>527002
No you don't need AutoCAD. Something simple like this just use sketchup it's free and for something crude you wouldn't need all the details, sketchup is more than capable.
I suggest you do a few draft overhead plans to get an idea of the layout and look at photos of train stations for reference.
How complicated you want it is up to you. A simple small station that trains just pass through would be really simple. If you need all the junctions gonna get much more complicated but I don't know enough about train stations to help you